Multi-stage absorption refrigeration system

ABSTRACT

There is provided an improved multi-stage absorption refrigeration system employing a highly concentrated solution of refrigerant to obtain an increased refrigeration effect relative to the quantity of input heat to the system as compared with a conventional system, comprising a multi-stage regeneratorcondenser system and at least a one-stage evaporator-absorber system provided with a pressure elevating device therebetween.

United States Patent 1 n 11 3,831,397

Mamiya 1 Aug. 27, 1974 [54] MULTI-STAGE ABSORPTION 2,446,988 8/1948 Flukes et a1, 62/483 REFRIGERATION SYSTEM 3,137,144 6/1964 Kaufman et al. 62/141 v 3,273,350 9/1966 Taylor 62/101 [76] Inventor: Gohee Mamiya, 11-6 Mltsuza a 3,651,655 3/1972 Dyre 62/476 Kamicho, Kanagawa-ku, 3,717,007 2/1973 Kuhlenschmidt 62/483 X Yokohama, J apan [22] Filed: May 1, 1973 Primary Examiner-William F. ODea [2]] pp No 356 0 Assistant Examiner-Peter D. Ferguson Related US. Application Data [63] Continuation-impart of Ser. No. 180,640, Sept. 15,

1971, Pat. NO. 3,742,728.

[52] US. Cl 62/476, 62/483, 62/489, 1 62/497 [51] Int. Cl. F25b 15/06 [58] Field of Search 62/101, 476, 483, 489, 62/497 [56] References Cited I UNITED STATES PATENTS 1,109,923 9/1914 Hiller 62/10] [57] ABSTRACT There is provided an improved multi-stage absorption refrigeration system employing a highly concentrated solution of refrigerant to obtain an increased refrigeration effect relative to the quantity of input heat to the system as compared with a conventional system, comprising a multi-stage regenerator-condenser system and at least a one-stage evaporator-absorber system provided with a pressure elevating device therebetween 6 Claims, 5 Drawing Figures MULTl-STAGE ABSORPTION REFRIGERATION SYSTEM This application is a continuation-in-part of copend ing application, Ser. No. 180,640, filed Sept. 15, 197l, now US. Pat. No. 3,742,728, issued July 3, 1973.

, In this evaporator-absorber system, the refrigerant from said regenerator-condenser system is vaporized in the evaporator, subsequently increased in pressure through the pressure elevating device and then absorbed at the increased pressure in the absorber.

The present invention relates to an absorption refrigeration system, particularly a multi-stage absorption refrigeration system employing a highly concentrated solution of refrigerant and has as its objective the provision of such system in an improved form of greater efficiency, that is, a greater refrigeration effect relative to the quantity of heat energy supplied to the system than the conventional system.

In accordance with the invention, there is provided a multi-stage absorption refrigeration system comprising a multi-stage regenerator-condensor system and at least a one-stage evaporator-absorber system provided with a pressure elevating device therebetween, wherein the refrigerant regenerated from the concentrated refrigerant solution in the regenerator-condenser system The invention will be described in detail with reference to the accompanying drawings, wherein:

FIG. 1 is a schematically illustrated flow diagram for a multi-stage absorption refrigerator according to the invention,

FIG. 2 is a diagram showing the cycle of refrigerant vapor and solution in the apparatus of FIG. 1 with reference to pressure, temperature and concentration,

FIG. 3 is a schematically illustrated flow diagram for another multi-stage absorption refrigerator according to the invention,

P16. 4 is a diagram showing the cycle of refrigerant vapor and solution in the apparatus of FIG. 3 with reference to pressure, temperature and concentration; and

FIG. 5 is a schematically illustrated flow diagram of v a multi-stage absorption refrigeration system that is a modification of the system of FIG. 3.

HO. 1 shows one of the embodiments of the multistage absorption refrigerator according to the invention, which has six stages of regenerators and condensers. The apparatus comprises regenerators l to 6, condensers 7m 12, an evaporator 13, a pressure elevating device 14 and an absorber 15. Part of a concentrated refrigerant soltuion is delivered through line 16 to the first regenerator 1, where his heated by a vaporous external heat source which is supplied to heater l8 disposed in the regenerator 1 through line 17, thereby regenerating a refrigerant vapor from the solution and thus producing a diluted residue of the refrigerant solution. The diluted residue in the first regenerator 1 then passes through outlet 19 to heat exchanger 20, while the refrigerant vapor regenerated in the first regenerator 1 passes through outlet 21 to the condenser 7 disposed in the second regenerator 2 and heats thereby another part of the concentrated refrigerant solution delivered to the second regenerator 2 through line 22 to regenerate a refrigerant vapor from the heated solution, whereby it is condensed to a liquid which subsequently passes to the heat exchanger through outlet 23. The diluted residue of the refrigerant solution from which the refrigerant vapor has been regenerated in the second regenerator 2 passes to heat exchanger 25 through outlet 24. The refrigerant vapor in the second regenerator 2 passes through outlet 26 to the condenser 8 disposed in the third regenerator 3 and heats thereby a further partof the concentrated refrigerant solution which has been flashed into the third regenerator through line 27 to regenerate a refrigerant vapor from the solution, whereby it is condensed into a liquid which subsequently passes to the heat exchanger 25 through outlet 28. A diluted residue of the refrigerant solution from which the refrigerant vapor has been regenerated in the third regenerator 3 passes through outlet 29 to heat exchanger 30. The refrigerant vapor in the third regenerator 3 passes through outlet 31 to the condenser 9 disposed in the fourth regenerator 4 and heats thereby another part of the concentrated refrigerant solution which has been delivered to the fourth regenerator 4 through line 32 to regenerate a refrigerant vapor from the solution, whereby it is condensed into a liquid which subsequently passes to the heat exchanger through outlet 34.

ln each following regenerator 4, 5, 6 such processes as described above are also carried out. However, the refrigerant vapor produced in the final regenerator 6 is introduced through outlet 46 to a condenser 12 in a evaporative condenser 47 or a condenser of a cooling water type to condense it into a liquid which subsequently passes through line 48 to flow into the combined line 69. On the other hand, the remaining refrigerant at high temperature produced in the regenerators excluding the sixth regenerator 6 is cooled in the heat exchangers 20, 25, 30, and by the parts of the concentrated refrigerant solution which are distributed from the absorber 15 to the regenerators through outlet 49, pump 50, line 51 and distributing lines 52 to57, the heat exchangers and then lines 16, 22, 27, 32, 37 and 42 respectively.

Each cooled refrigerant flows through each reducing valve 64, 65, 66, 67 or 68 into the combined line 69 together with the refrigerant from the condenser 12. Tl-le confluent flow of the refrigerant through line 69 is introduced at a reduced pressure through reducing valve 70 to the evaporator 13, so that it is vaporized at a low temperature corresponding to its reduced pressure maintained in evaporator 13, thereby creating the target refrigeration effect for cooling a fluid passing through a heat exchanger 71 disposed in the evaporator '13. On the other hand, the dilute refrigerant solutions which have-been cooled through the respective heat exchangers 20, 25, 30, 35, 40 and are reduced in pressure through the respective reducing valves 72 to 77 and flow into the combined line 78. The combined solution is reduced in pressure through reducing valve 79 and then is flashed into the absorber 15.

The refrigerant vapor produced by the refrigeration effect in the evaporator 13 is transferred through the pressure elevating device 14 to the absorber 15 in which it is absorbed by the dilute refrigerant solution flashed into the absorber. The heat generated by the absorption at this time is absorbed by cooling water which passes through cooler 80 disposed in the absorber 15.

in conventional apparatus, evaporators such as evaporator 13 and absorbers such as absorber l maintain the refrigerant vapor at constant pressure. The apparatus according to this invention employs a more highly concentrated refrigerant solution for obtaining a greater refrigeration effect than conventional apparatus. Therefore, in a case where the vapor is passed to the absorber without a pressure increase from the pressure elevating device 14 thetemperature of the dilute refrigerant solution in the absorber must be lowered to effect the same degree of absorption. However, it is difficult to obtain such lower temperature by applying cooling water such as well water or water supplied from a cooling tower.

ln view of this fact, a pressure elevating device 14 such as an electric fan connecting the evaporator 13 and the absorber 15 therewith is provided in this invention. In the arrangement, the refrigerant vapor produced as a result of the evaporation for creating the refrigeration effect in the evaporator 13 is fed through passage 81 to the pressure elevating device 14, where it is increased in pressure and then at the higher pressure is introduced through passage 82 to the absorber 15 which is maintained at the same high pressure. In other words, pressure elevating device 14 is provided for introducing the refrigerant vapor at a higher pressure corresponding to the temperature of the solution in the absorber which temperature may be attained easily by applying cooling water such as previously described.

The refrigerant vapor thus introduced into the absorber 15 is absorbed effectively by the dilute refrigerant solution which has been fed to the absorber 15 through the reducing valve 79, whereby the dilute refrigerant solution is converted into a concentrated refrigerant solution. The concentrated refrigerant solution is discharged from outlet 49 of the absorber through line 51 to pump 50 disposed therein, by which it is pressurized. The pressurized solution is distributed to the regenerators l to 6 through distributing lines 52 to 57, the first heat exchangers 20, 25, 30, 35, 40 and 45, regulating valves 58 to 63 and second heat exchangers 83 to 88, respectively. On the way to the regenerators the respective solutions are heated by the first heatexchangers and then supplementally heated by the second heat exchangers up to the necessary temperature for effecting their subsequent vaporization in the regenerators as previously described.

The refrigeration effect thus is obtained by repeating the cycle operation set forth above in the refrigerator.

.FIG. 2 illustrates a cycle of a refrigerant solution with reference to pressure, temperature and concentration in the case where water is used as a refrigerant material and a water-lithium bromide solution is used as the refrigerant solution in the apparatus shown in FIG. 1.

Concentrations referred to hereinafter and in the drawings are those for lithium-bromide in weight by percent in the refrigerant solution.

In this example, a 45 percent solution of lithium bromide is distributed from the absorber to the respective regenerators wherein the distributed solution is vaporized up to a 50 percent solution, and the resultant solutions are subsequently returned to the absorber 15 after they are cooled by the heat exchangers 20, 25, 30, 35, 40 and 45.

Referring to FIG. 2, the first 45 percent solution at a pressure of 30.1588 atm., at a temperature of 258C corresponding to point A is introduced into the first regenerator 1, where it is heated to 267C at point 8,, and thus a refrigerant vapor at 233C at point C 1 is generated from it, whereby it is concentrated to a 50 percent solution, where is a dilute refrigerant solution. The second 45 percent solution at a pressure of 125302 atm. and at a temperature of 214C corresponding to point A; is introduced into the second regenerator 2, where it is heated to a temperature of 223C at point B by the latent heat of condensation of the regenerated vapor introduced from the first regenerator at a temperature of 233C at the point C, and thus a refrigerant vapor is regenerated from it at a temperature of 189C at point C whereby it is concentrated to a 50 percent solution as a dilute refrigerant solution.

In such processes as described above, the third, fourth, fifth and sixth 45% solutions corresponding to points A A A and A are introduced into the respective regenerators, where they are heated to the temperatures shown at points B B B and B by the latent heat of condensation of the regenerated vapors introduced from the loading regenerators corresponding to points C C C and C respectively and thus refrigerant vapors corresponding to C C C and C are respectively regenerated from them, whereby they are concentrated to 50 percent solutions as dilute refrigerant solutions. Subsequently, the regenerated vapors excluding C are condensed to liquids and then cooled to a temperature of 40C by the heat exchangers 20, 25, 30, 35 and 40 respectively, while the remaining vapor C is condensed at a temperature of 35C to a liquid at the same temperature by the evaporative condenser 47.

All the condensed refrigerants flow into the evaporator through line 69 and then the combined liquid refrigerant is vaporized under the conditions corresponding to point D to create the refrigeration effect.

For effecting the absorption of the resultant vapor by the 50 percent solution in the absorber under the same pressure as the evaporator, it would be necessary for the solution in the absorber to be cooled to a temperature below 20C. However, according to the invention, the pressure of the refrigerant vapor corresponding to the point D is raised to the pressure corresponding to point E by the pressure elevating device 14 and introduced into the absorber 15 which is maintained at the same elevated pressure, while the 50 percent solution is introduced from the respective regenerators to the absorber in a combined flow through the line 78 after being cooled by the respective heat exchangers. In this connection, the refrigerant vapor is absorbed by the dilute refrigerant solution of 50 percent lithium bromide under the conditions corresponding to point F so as to change it to a concentrated refrigerant solution of 45 percent lithium bromide. Therefore, the above absorption process may be carried out effectively if the solution in the absorber is cooled to a temperature of 35C or lower.

Alternatively, when the refrigerant vapor is pressurized to a pressure at the point E, the refrigerant vapor may be absorbed by the 50 percent colution in the absorber at the same pressure. In this case, an effective absorption would be carried out by cooling the solution in the absorber to a temperature of 45C or lower which may be attained more easily than in the former case.

In this example, if the 45 percent solutions introduced into the regenerators 1 to 6 are 10,000 kg/h, 7,437 kg/h, 5,336 kg/h, 4,703 kg/h, 3,854 kg/h and 3,250 kg/h respectively, the regenerated refrigerants in the regenerators amount to 1,000 kg/h, 743.7 kg/h. 583.6 kg/h, 470.3 kg/h, 385.4 kg/h and 325 kg/h, respectively. The total amount of the regenerated refrigerant is 3,508 kg/h, so that the corresponding total refrigeration capacity is equivalent to 1,963,647 Kcal/h. The substantial refrigeration capacity becomes 1,767,282 Kcal/h (196,364 X 0.9), assuming that the heat exchanging efficiency in the heat exchanger 71 is 0.9.

The total quantity of heat externally supplied to the heaters 18 and 83 to 88 is 836,354 Kcal/h, assuming that the heat exchanging efficiency of each heater is 0.9. Of the total quantity of the input heat, the heater 18 disposed in the first regenerator 1 requires a quantity equivalent to 539,855 Kcal/h and the respective heaters 83 to 88 for heating supplementally the dilute refrigerant solutions require quantities equivalent to 1205288 Kcal/h, 75,521 Kcal/h, 49,4698 Kcal/h, 29,4102 Kcal/h, 14,7366 Kcal/h and 6,832.2 Kcal/h, which amount to 296,499 Kcal/h. v Accordingly, the ratio of the refrigeration capacity to the total quantity of the input heat is as follows.

1,767,282 Kcal/h 836,354 Kcal/h =21 1.3 100 The conventional absorption refrigerator provides a refrigeration capacity of 70 Kcal/h relative to an input heat of 100 Kcal/h. Comparing the refrigerator according to the present invention with the conventional refrigerator the former has a refrigeration capacity approximately three times greater (21 1.3/70 3.01

FIG. 3 shows a diagram of another embodiment of the refrigerator according to the present invention wherein the refrigerant solution is circulated successively through all the refrigerators in series.

In the refrigerator shown in FIG. 3, 21 concentrated refrigerant solution is introduced through line 113 and valve 109 from a central heat exchanger 125 to a first regenerator 101, where it is heated by an external heat source supplied to heat exchanger 126 disposed in the first regenerator, thereby regenerating a refrigerant vapor and thus producing a dilute residue. The resultant solution with the lower concentration of the refrigerant is fed to a second regenerator 102 through line 117 passing through the heat exchanger 125 and through valve 110, while the resultant vapor is fed to condenser 105 disposed in the second regenerator 102 through line 121.

On the way to the second regenerator 102, the dilute refrigerant solution is cooled to the necessary temperature by the heat exchanger 125. The refrigerant vapor passing through the condenser 105 heats the dilute solution flashed into the second regenerator 102 from the first regenerator 101 by its heat of condensation to regenerate a refrigerant vapor from the solution and produce a diluted residue thereof, whereby it is condensed to a refrigerant liquid. The diluted residue of the solution in the second regenerator 102 with lower concentration of the refrigerant than in the first regenerator 101 is introduced to a third regenerator 103 through line 118 passing through the heat exchanger 125 and through valve 111, while the regenerated vapor is fed to a condenser 106 disposed in the third regenerator 103 through line 122.

On the way to the third regenerator, the lower concentrated solution is cooled to the necessary temperature by the heat exchanger 125. The refrigerant vapor in the condenser 106 heats the lower concentrated solution flashed into the third regenerator 103 to regenerate a refrigerant vapor from the solution and produce a diluted residue thereof, whereby it is condensed to a refrigerant liquid. The diluted residue of the solution with lower concentration of the refrigerant than in the second regenerator is introduced to a fourth regenera-,

tor 104 through line 119 passing through the heat exchanger 125 and through valve 112, while the refrigerant'vapor is fed to condenser 107 disposed in the fourth regenerator 104 through line 123. On the way to the fourth regenerator, the lower concentrated solution is cooled to the necessary temperature by the heat exchanger 125.

The refrigerant vapor in the condenser 107 heats the lower concentrated solution flashed into the fourth regenerator to regenerate a refrigerant vapor from the solution and to produce diluted residue thereof, whereby it is condensed to a refrigerant liquid. The diluted residue of the solution with the lower concentra-' tion of the refrigerant than in the third regenerator is passed to the heat exchanger 125 through line 120 to be cooled to the necessary temperature, while the refrigerant vapor is passed through line 124 to heat exchanger 108, where the vapor is condensed to a refrigerant liquid.

The refrigerant condensed in the condenser 108 and the other refrigerant cooled in the heat exchanger 125 may be combined as a fluid to be subsequently vaporized for creating a refrigeration effect and then absorbed at an increased pressure of the resultant vapor in a single stage of the evaporator and the absorber which are connected to the pressure elevating device as shown in FIG. 1. However,-in the embodiment shown in FIG. 3, the respective. refrigerants are to be processed for effecting evaporation, pressurization and then absorption in the respective stages of the units, each of which comprises an evaporator, a pressure elevating device and an absorber. In this embodiment, a more complicated system is required, while the necessary energy for driving the pressure elevating device is lower in comparison with the embodiment of FIG. 1.

The evaporation and absorption processes in FIG. 3 are now explained in detail as follows.

The respective refrigerants regenerated in the regenerators and then condensed in the condensers are fed through reducing valves 131 to 134 to evaporators 127 to 130, where they are vaporized to create the refrigeration effect for cooling fluids passing through respective heat exchangers 147 to 150 disposed in the evaporators. The resultant vapors then pass through pressure elevating devices 135 to 138 and are introduced at the increased pressure to absorbers 139 to 142, respectively.

The dilute refrigerant solution from the final regenerator 104 is flashed into the first absorber 139 through reducing valve 155 and then absorbs the pressurized vapor which has been introduced from the first evaporator 127 to the absorber at the same pressure through the pressure elevating device 135.

The resultant solution in the first absorber 139 is then introduced through pump 143 and reducing valve 156 to the second absorber 140, where it absorbs the vapor which has been produced in the second evaporator 128 and then increased in pressure by the pressure elevating device 136. The resultant solution in the second absorber 140 is then introduced via pump 144 and reducing valve 157 to the third absorber 141, where it absorbs the vapor which has been produced in the third evaporator 129 and then pressurized by the pressure elevating device 137. The resultant solution in the third absorber 141 is then introduced through pump 145 and reducing valve 158 to the fourth absorber 142, where it absorbs the vapor which has been produced in the fourth evaporator 130 and then elevated in pressure by the pressure elevating device 138. The resultant concentrated solution of the refrigerant in the final ab sorber 142 is fed to the central heat exchanger 125 through pump 146 and line 159.

In the heat exchanger 125, the concentrated solution is heated and passed to the first regenerator 101 through line 113 and thus the process of the refrigerant solution from the first regenerator 101 to the fourth regenerator 104 is repeated as previously set forth for creating the refrigeration effects in the respective evaporators.

The refrigerant solutions in the respective absorbers 139 to 142 are cooled by cooling water passing through coolers 151 to 154 disposed therein.

FIG. 4 shows an example of the cycle of the refrigerant solution with reference to pressure, temperature and concentration, when water is used as a refrigerant material and a water-lithium bromide solution is used as the refrigerant solution in the apparatus shown in FIG. 3.

The concentrations shown in FIG. 4 indicate those of lithium bromide in weight by percent in the solution.

Referring to FIG. 4, when the aqueous solution of lithium bromide corresponding to point A is introduced to the first regenerator 101 and heated therein, a refrigerant vapor of wator corresponding to point C 1 is regenerated from the solution. The diluted residue of the solution at B is cooled by the heat exchanger 125, reduced in pressure by the reducing valve 110 and fed to the second regenerator 102 under the condition corresponding to point A When the solution at A is heated by the refrigerant vapor at C 1 to be given a latent heat of condensation thereby,'it regenerates a refrigerant vapor corresponding to point C whereby it is changed to a solution corresponding to point B By successively carrying out such processes as the above in order to change the state of the refrigerant solution from that at point B to the state at points A;,, B A and finally B refrigerant vapors corresponding to points C and C are obtained.

The refrigerant at the point C is condensed into liquid which is subsequently vaporized in the first evaporator 127 under the condition corresponding to point G, thereby creating a refrigeration effect. The resultant vapor is increased in pressure at point E through the pressure elevating device 135 and thus introduced to the first absorber 139, where his absorbed by the refrigerant solution introduced through a valve 155 at point D, whereby a concentrated solution at point F i is produced.

The refrigerant at the point C is condensed into a liquid which is subsequently vaporized in the second evaporator 128 under the condition corresponding at the point G, thereby creating a refrigeration effect. The resultant vapor is increased in pressure at point E through the pressure elevating device 136 and thus introduced to the second absorber 140, wherein it is absorbed by the refrigerant solution introduced from the first absorber 139, whereby a more concentrated solution at point F is produced. By successively carrying out such processes as described above, the refrigerants at the points C and C are also vaporized in the third and the fourth evaporators 129 and 130 under the conditions at the point G, and more concentrated solutions at points F and F are produced in the third and the fourth absorbers 141 and 142, respectively.

The final concentrated solution at the point P in the final absorber 142 is then passed to the heat exchanger 125 via the pump 146 and the line 159.

When a 43.9 percent aqueous solution of lithium bromide at a pressure of 13.97 atm. and at a temperature of 217C corresponding to the point A is introduced into the first regenerator 101 from the heat exchanger 125 at a flow rate of l0,000 kg/h and the cycle operation as shown in FIG. 4 is carried out, quantites of heat of 565,181.23 Kcal/h and 35,4673 Kcal/h (i.e. total amount of 600,649.l Kcal/h) are required to be supplied to the heat exchanger 126 and 160 respectively, whereby a refrigeration effect equivalent to 1,340,684.3 Kcal/h is obtained overall. The refrigeration capacity obtained is thus 223.2 Kcal/h relative to an input heat to the system of 100 Kcal/h (1340,6843 600.6491 X 100 223.2).

The conventional absorption refrigerator provides a refrigeration effect of Kcal/h relative to a supplied quantity of heat of Kcal/h. Comparing the illustrated apparatus of the present invention with a conventional refrigerator, it has a refrigeration capacity approximately 3.19 times that of the conventional refrigerator (223.2 70 3.19).

FIG. 5 illustrates a diagram of a further embodiment of the refrigerator according to the present invention wherein the regenerator-condenser system is arranged successively in the manner of the embodiment of FIG. 3. Portions of the embodiment of FIG. 5 corresponding to those of FIG. 3 as above described are hence provided with the same reference numerals.

Referring now to FIG. 5, a concentrated refrigerant solution is introduced by way of line 113 and valve 109 from a central heat exchanger 125 to a first regenerator 101, where it is heated by an external heat exchanger source supplied to the heat exchanger 126 disposed in the first regenerator, in order to regenerate a refrigerant vapor'and produce a dilute residue. The resultant solution having a lower concentration of refrigerant is applied to the second regenerator 102 by way of line 117, which passes through the heat exchanger 125, and the valve 110. The vapor in the regenerator 101 is applied to the condenser in the regenerator 102 by way of line 121. Further, as in the arrangement of FIG. 3, dilute refrigerant solution from the regenerator 102 is applied to the regenerator 103 by way of line 118 passing through the heat exchanger and valve 111, and dilute refrigerant solution from the regenerator 103 is applied to the regenerator 104 by way of line 119 also passing through the heat exchanger 125 and the valve 112. Similarly, vapor from the second regenerator 102 is passed by way of line 122 to the condenser 106 in the regenerator 103, and vapor from the regenerator 103 is applied by way of line 123 to the condenser 107 in the regenerator 104. The arrangement of FIG. is provided with a single evaporator 170, a single absorber 171, and a pressure elevating device 172 is provided for applying refrigerant vapor from the evaporator 170 to the absorber 171. Vapor from the regenerator 104 is passed by way of line 173 to a condenser 174 in an evaporative condenser 175 or a condenser of a cooling water type to condense it into a liquid which is subsequently passed by way of line 176 and reducing valve 177 to the evaporator 170, so that it is vaporized therein at a low temperature corresponding to its reduced pressure maintained in the evaporator 170. Dilute residue from the regenerator 104 is passed in line 120 through the heat exchanger 125 and by way of the reducing valve 178 to the absorber 171, wherein the dilute residue is flashed. Heat generated by absorption in the absorber is absorbed by cooling water which passes through the cooler 179 disposed within the absorber 171. The concentrated solution of refrigerant in the absorber 171 is pumped to the central heat exchanger 125 by way of pump 180 and line 181.

Refrigerants regenerated in the regenerators 102, 103 and 104 and condensed in the condensers 105, 106, and 107 are fed by way of lines 182, 183, and 184 respectively to join the line 176, by way of reducing valves 185, 186 and 187 respectively. The lines 182, 183 and 184 pass through the heat exchanger 125.

The arrangement of FIG. 5 operates in a manner similar to that of the arrangement of FIG. 3 as above described.

According to the invention, since a more highly concentrated solution of refrigerant is employed than in the conventional refrigerator, a vapor is generated with a considerably higher temperature than in the conventional refrigerator for the same temperature of the refrigerant solutions. For example, in the embodiment shown in FIG. 2, vapor at a temperature of 233C is regenerated from a 50 percent solution of lithium bromide at a temperature of 267C, while vapor at a temperature of 195C (at point C is regenerated from a 65 percent solution at a temperature of 267C.

In view of this fact, a system of the multistage type according to the invention is distinguishably suitable for employing a more concentrated refrigerant solution, thereby obtaining a greater refrigeration effect than heretofore known.

Further, according to the present invention, even if an aqueous solution of lithium bromide is'employed as a refrigerant solution, crystallization of lithium bromide will not occur under the lower temperature employed in thepresent system, because the concentration of lithium bromide employed is lower than in the conventional system.

What is claimed is:

1. An absorption refrigeration system comprising a plurality of successive regenerator condensor vessels each having a heat exchange therein,

an evaporator system,

an absorber system,

and a highly concentrated refrigerant solution therein,

said system further comprising means for applying heat to the heat exchanger of a first one of said vessels,

means for passing concentrated refrigerant solution from said absorber system to said first one of said vessels for absorbing heat from the heat exchanger therein to regenerate a refrigerant vapor and a dilute residue of solution therein,

means for passing dilute residue from all but a second of said vessels to a succeeding vessel for absorbing heat from the heat exchanger in the respective succeeding vessel to regenerate a refrigerant vapor and a dilute residue of solution therein,

means for passing refrigerant vapor from all but said second vessel to the heat exchanger of a succeeding vessel,

means for condensing vapor from said second vessel to a liquid,

means for passing liquid from said means for condensing and from said heat exchanger of all but said first vessel to said evaporator system for vaporization therein,

means for passing dilute residue from said second vessel to said absorber system,

and means for increasing the pressure of vapors in said evaporator system and applying them to said absorber system for absorption therein. I

2. The absorption refrigeration system of claim 1 wherein said evaporator system comprises a single evaporator, and said absorber system comprises a single absorber.

wherein said means for passing concentrated refrigerant solution from said absorber system comprises means for passing concentrated refrigerant solution from said absorber in heat transfer with said means for passing liquid from said heat exchangers to said evaporator system and in heat transfer relationship with said means for passing dilute residue from said vessels to a succeeding vessel, to said first one of said vessels.

4. The absorption refrigeration system of claim 1 wherein said evaporator system comprises a plurality of evaporators and said absorber system comprises a plurality of absorbers, said means for increasing the pressure of said vapors comprising separate pressure elevating means interconnected in each evaporator with a separate absorber to form a plurality of evaporator absorber units, further comprising means for passing concentrated solution of refrigerant produced in all but a last one of said units successively from a first of said units to the absorber of a succeeding one of said units, said means for passing concentrated refrigerant solution from said absorber system comprising means for passing concentrated refrigerant solution from the absorber of said last unit to said first vessel, said means for passing liquid comprising means for passing liquid in succeeding order from the heat exchanger of said vessel next succeeding the first vessel to the evaporators of said units in an order succeeding from said last unit, and means for passing liquid from said means for condensing to the evaporator of said first unit, said means for passing dilute residue from said second vessel comprising means for passing dilute residue from said second vessel to the absorber of said first unit.

5. The absorption refrigeration system of claim 4 comprising means for passing said concentrated refrigerant solution from the last absorber in heat transfer relationship to said means for passing liquid in succeeding order and in heat transfer relationship to dilute residue passed from each of said vessels.

6. The absorption refrigeration system of claim 1,

said vessels comprises a water-lithium bromide solution having a water concentration in excess of 4 5 percent by weight or a lithium bromide concentration less than wherein the concentrated refrigerant solution to be 5 55 Percent y Weight- 

1. An absorption refrigeration system comprising a plurality of successive regenerator condensor vessels each having a heat exchange therein, an evaporator system, an absorber system, and a highly concentrated refrigerant solution therein, said system further comprising means for applying heat to the heat exchanger of a first one of said vessels, means for passing concentrated refrigerant solution from said absorber system to said first one of said vessels for absorbing heat from the heat exchanger therein to regenerate a refrigerant vapor and a dilute residue of solution therein, means for passing dilute residue from all but a second of said vessels to a succeeding vessel for absorbing heat from the heat exchanger in the respective succeeding vessel to regenerate a refrigerant vapor and a dilute residue of solution therein, means for passing refrigerant vapor from all but said second vessel to the heat exchanger of a succeeding vessel, means for condensing vapor from said second vessel to a liquid, means for passing liquid from said means for condensing and from said heat exchanger of all but said first vessel to said evaporator system for vaporization therein, means for passing dilute residue from said second vessel to said absorber system, and means for increasing the pressure of vapors in said evaporator system and applying them to said absorber system for absorption therein.
 2. The absorption refrigeration system of claim 1 wherein said evaporator system comprises a single evaporator, and said absorber system comprises a single absorber.
 3. The absorption refrigeration system of claim 2 wherein said means for passing concentrated refrigerant solution from said absorber system comprises means for passing concentrated refrigerant solution from said absorber in heat transfer with said means for passing liquid from said heat exchangers to said evaporator system and in heat transfer relationship with said means for passing dilute residue from said vessels to a succeeding vessel, to said first one of said vessels.
 4. The absorption refrigeration system of claim 1 wherein said evaporator system comprises a plurality of evaporators and said absorber system comprises a plurality of absorbers, said means for increasing the pressure of said vapors comprising separate pressure elevating means interconnected in each evaporator with a separate absorber to form a plurality of evaporator absorber units, further comprising means for passing concentrated solution of refrigerant produced in all but a last one of said units successively from a first of said units to the absorber of a succeeding one of said units, said means for passing concentrated refrigerant solution from said absorber system comprising means for passing concentrated refrigerant solution from the absorber of said last unit to said first vessel, said means for passing liquid comprising means for passing liquid in succeeding order from the heat exchanger of said vessel next succeeding the first vessel to the evaporators of said units in an order succeeding from said last unit, and means for passing liquid from said means for condensing to the evaporator of said first unit, said means for passing dilute residue from said second vessel comprising means for passing dilute residue from said second vessel to the absorber of said first unit.
 5. The absorption refrigeration system of claim 4 comprising mEans for passing said concentrated refrigerant solution from the last absorber in heat transfer relationship to said means for passing liquid in succeeding order and in heat transfer relationship to dilute residue passed from each of said vessels.
 6. The absorption refrigeration system of claim 1, wherein the concentrated refrigerant solution to be passed from said absorber system to said first one of said vessels comprises a water-lithium bromide solution having a water concentration in excess of = 45 percent by weight or a lithium bromide concentration less than 55 percent by weight. 